I Sweat, Therefore I Lose Weight?
Spending a day at the spa is definitely one of my favorite activities! Alternating between the sauna and freezing cold bath helps me let off some steam. And what to say about the beauty of the place! It is also said that these hot-cold cycles help eliminate stress, relax muscles, improve blood flow, and even lose weight! There is no doubt about one thing: it doesn’t make us lose fat, but water.
What happens when you sweat?
First, you need to know that your body is an enormous water reserve, as 65 % of your body is made of water . This means that the body of a 150 lb person contains 100 pounds of water!
Water plays many functions, and one of the most important is maintaining the temperature of the organism. Even in a sauna where the temperature can go up to 90 °C, your body stays at 37 °C. All this thanks to perspiration.
Indeed, when you are hot, your body transfers its heat to the water in your cells. This water is then expelled through the skin in the form of sweat.
Perspiration = weight loss?
The answer is yes. When we sweat, we lose weight, but not necessarily fat! In fact, to lose weight we need to burn calories. And to lose calories, we need to move!
When you are active, the cells of your body become some sort of little furnaces and produce a lot of heat. By moving, you ask your body to feed these little furnaces with carbs and fat. This is what makes you spend calories and lose weight. Perspiration is simply a way to evacuate the heat produced by the furnaces.
In a sauna, you stay put, and you sweat. This is because the temperature in the room forces your body to expel more heat through your sweat. However, since there is no furnace to feed, no calories are burned!
In short, when you see the number on the scale going down after a sauna session, remember that you are simply slightly dehydrated. By the way, the principle behind infratherapy and sweat belts promising effortless weight loss is the same. Do not forget the old saying: “If it seems too good to be true, it probably is.”
1. Ledoux M, St-Martin G, Lacombe N. 2009. Nutrition, sport et performance. 2e éd. Québec: Vélo Québec Éditions, p. 67.